My laboratory focuses on the prominent players in the adaptive and allergic response, the CD4 T cell, with two approaches. First, we are interested in the mechanism by which inhibitors of "drug pumps" such as MRP1 inhibit T cell activation. We hypothesize that these studies will reveal novel drug targets for treatment of T cell mediated autoimmunity, including allergic diseases and asthma. Second, we are investigating the functional response to the Respiratory Syncytial Virus (RSV). Epidemiological and animal studies suggest that childhood asthma and atopy are sequelae of severe RSV disease in infancy. While a genetic predisposition towards asthma is likely necessary, RSV uniquely appears to tip the balance towards chronic and episodic childhood wheezing and perhaps adult asthma as well. In contrast to children, adults tolerate RSV infection without wheezing. Dissection of the T cell response by children to RSV to determine the unique features that might bias the immune response towards atopy and pulmonary hypersensitivity. Characterization of the adult response will identify ideal characteristics of the T cell response to viral vaccines. These findings may contribute towards the design of an immunogenic but not "atopigenic" RSV vaccine, and towards the acquisition of surrogate markers that will address efficacy of any vaccines designed to enhance T cell responses, including vaccines for HIV. Finally, we are by characterizing the T cell responses to RSV in adults. Identification of multifunctional memory CD4 T cells that effectively suppress chronic and recurrent viral infections. Almost all children have been infected with RSV by the age of 2 years, some more than once. RSV infection is the most common event that precipitates wheezing in children and response to RSV in infancy strongly predicts the presence of childhood asthma. Thus, characterizing the T cell response to RSV may provide insight towards understanding childhood asthma. To that end, there are two experimental projects planned. The first is to define the T cell responses to RSV and other respiratory viruses by tonsil T cells. Tonsils are in an ideal anatomic location for RSV antigen presentation, and thus should contain an abundance of RSV specific cells. The studies will be done with cells in suspension, and with tonsil histocultures. Histocultures are an excellent model to study RSV specific responses because anatomic structure and cellular composition are intact. Furthermore, use of a GFP-expressing virus allows tracking of infected cells and the immune response to RSV. Clinical histories of the tonsil donors will allow correlation of immune responses with asthma. The second project addresses the need for immunological correlates of protection to viruses to which neutralizing antibodies are insufficient or irrelevant. In these cases (such as RSV and HIV) protection is dependent upon memory CD4 T cells, independent of their role as B cell helpers. It is not known, however, which subsets of memory CD4 T cells are best equipped for protection. Multiple memory cell subsets have been recently defined based on their expression of chemokine receptors and other homing receptors in combination with CD45 isoforms. The recent development of 10-12 parameter flow cytometry and cell sorting will allow subsets to be functionally defined and characterized, which in turn may be applied to clinical vaccine studies to determine correlates of protection. These results may be used to guide vaccine development in any case where cellular responses serve a critical role in protection. The role of multidrug resistant proteins in modulation of the adaptive immune response. Members of the MDR and MRP families of proteins are expressed on T cells, and T cell function appears to depend upon these "drug pumps." We have found that inhibition of one member of this family blocks cytokine secretion in response to T cell receptor stimulation. Since allergic diseases are mediated by CD4 T cells and type 2 cytokines such as IL-4 and IL-13, modulation of T cell function by inhibiting relevant drug pumps such as MRP1 may be a novel approach towards treating allergic diseases. This project incorporates FY2002 projects 1Z01BJ008008-02 and 1Z01BJ008009-01.